Due to the modularized design feature of the distributed base station, the distributed base station has advantages of standardized interfaces, convenient addressing and convenient system extension and upgrade, which complies with the future development trend of the novel mobile networks. Especially, it is widely applied in Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems.
In the TD-SCDMA distributed networking scenario, as shown in FIG. 1, the TD-SCDMA distributed networking comprises a Base Band Unit (BBU) and a Radio Remote Unit (RRU), which are connected to each other via optical fiber or other means. In this case, the BBU is mainly used for realizing functions such as carrier frequency resource allocation, wireless link establishment, wireless link control, up/downlink signal modulation coding/decoding and so on in the TD-SCDMA systems; and the RRU is mainly used for transmitting an IQ modulation signal sent from the BBU as a TD-SCDMA air interface signal by a power amplifier unit through up-conversion, and for detecting and receiving a user signal, converting the user signal to an IQ modulation signal through down-conversion and sending the IQ modulation signal to the BBU for processing.
In the view of signal transformation, mobile communications rely on the transformation from baseband signals to radio frequency signals and the inverse process thereof. However, by taking the radio frequency performance as the measurement criteria of the radio frequency signal, the key performances of the mobile communication system are determined regarding aspects such as signal quality, signal coverage range, etc.
As to such Error Vector Magnitude (EVM) performance which can be described by an accurate mathematic model, the performance can be controlled well by improving the signal processing method regarding modulation and demodulation at the baseband side and improving peak cancellation processing at the radio frequency side, filter design, and so on, and the effects can last for a long time. Generally, the performance will not deteriorate with the change in the external environment over time.
However, as to some radio frequency performances, the mathematic models thereof usually are nonlinear and may have significant changes with the change in the external environment over time. As to the output power, in order to ensure the accuracy of the output of the air interface, the conventional approach is to carry out parameter measurement on a certain batch of power amplifiers by way of instrument measurement, approximately obtain a gain curve of the power amplifiers by way of the liner fitting method, and then store the curve in the format of table and so on; and the base station can call the relevant curve during operation, and then dynamically adjust and compensate to the output power, wherein the approach has the defects as follows.
First, since the gain curve is an average estimation of a certain batch of power amplifiers, the real gain feature of an individual power amplifier cannot be reflected accurately.
Second, since the conventional power control method is a model to carry out a rough adjustment using measurement experience values and then carry out a fine adjustment within in a small range. This method can only rely on the previously measured characteristic curves, and when the gain characteristic of the power amplifier itself has significant offset with the change in the external environment over time, this method cannot realize dynamic adjustments.
Therefore, such parameter as output power is easy to change randomly and dynamically with factors such as external environment, time, and so on, which result in that the radio frequency performance thereof is unstable, the accuracy of the power output of the air interface cannot be ensured, the signal modulation of the distributed base station is affected, and the distributed base station carries out the real-time adjustment on the radio frequency performance difficultly.